1.Cooperation between the needle and the swing shuttle

  When the needle is at the highest position(i.e. the turning angle is 0°), the shuttle is at the ultimate position clockwise, as shown in Fig.6, its off-line space is 4.5-6 and its outgoing line space is 2-2.5. when the needle and swing shuttle are at this relative position, it is good for the thread ring to come out and the tightness of thread trace.Fig.6 Guaranteed space for thread outtu图6 脱线应保证的间隙

  When the needle is at the lowest position(i.e. the turning angle is 180°), the swing shuttle is at the ultimate position counterclockwise. The drawing thread space is 6-7mm(tu图7 勾线时应保证的间隙) (shown in Fig.), and the outgoing line space is also 2-2.5mm. The position can ensure the thread formation and make it convenient for the thread ring to be put on the shuttle. In fact, because of the space between the shuttle and the swing shuttle bracket and the feature of sewing materials, as usual, the moving time of the needle is a little earlier than the swing shuttle, which is good for the formation of thread bubble and the swing shuttle tip into the thread ring.  Fig.7 Guaranteed space when drawing thread

2.Cooperation between thread-picking lever and needle and swing shuttle

    The thread-picking lever cooperates with the needle and the shuttle. When the upper shaft turns to 60°, the thread-picking lever begins to go down. When the needle falls to the lowest position and goes upward(180°--210°), the thread-picking lever should be still or fall slowly so as not to influence the formation of thread bubble. When the shuttle tip hooks the thread ring, the thread-picking should fall quickly and supply the amount of the thread to the thread ring. Otherwise, the thread will be too tight and even broken.